The photoheliograph was the first instrument designed for photographing the Sun and is essentially an elongated camera. This was one of five similar instruments made by Dallmeyer specially for the British Transit of Venus expeditions of 1874. It was used for taking a series of photographs of Venus crossing the Sun�s disc, in the hope that a permanent photographic record would overcome the problem of discrepant judgements between different observers. In the event, the analysis of the photographs presented its own problems. After the transit, this photoheliograph was returned to the Royal Observatory Greenwich and used to take regular photographs of the Sun until 1949.